AVG (Free). I just wish I could figure out how to hide/not display the update dialogue that pops up every time I boot Windows.
right click on the icon in the system tray (bottom right) and click 'launch control center'.
click on update manager in the right pane, and then click the 'properties' button.
uncheck the 'display information about update process' box near the bottom and the click ok. should kill the update pop-up.
oh, and yet another vote for AVG, it's good stuff. best of luck.